Oracle Database Flashback Technologies

Oracle Database Flashback Technologies is a comprehensive range of tools for data recovery solutions that reverse human and logical errors by selectively and efficiently undoing the effects of a mistake.

These features include Flashback Database, Flashback Table, and Flashback Query, each serving different purposes and having different dependencies

1. Flashback Query: Purpose: Allows querying historical data at a specific timestamp or SCN (system change number ). Dependency: depend on undo data and are influenced by the UNDO_RETENTION parameter. Enabling RETENTION GUARANTEE ensures undo data is retained for the specified period.
2. Flashback Table: Purpose: Allows reverting an entire table to a previous state. Dependency: depend on undo data and are influenced by the UNDO_RETENTION parameter. Enabling RETENTION GUARANTEE ensures undo data is retained for the specified period.
3. Flashback Database: Purpose: Rewinds the entire database to a previous point in time. Dependency: Uses flashback logs rather than undo data to restore the database. depends on flashback logs stored in the FRA and is not directly affected by undo retention.

Configuring Undo Retention :-

Undo retention is crucial for Flashback Query and Flashback Table. It determines how long undo data is retained before being overwritten.

ALTER SYSTEM SET UNDO_RETENTION = 3600;? -- Retain undo data for 1 hour

Enable Undo Retention Guarantee :-

ALTER TABLESPACE undotbs1 RETENTION GUARANTEE;

With RETENTION GUARANTEE, Oracle ensures undo data is not overwritten before the retention period, providing a reliable timeframe for Flashback operations.

Creating Guaranteed Restore Points :-

Enabling Flashback Database does not automatically create a guaranteed restore point. Guaranteed restore points must be created explicitly. Flashback logs and other recovery-related files are maintained in the FRA to support Flashback Database operations.

CREATE RESTORE POINT before_data_patch GUARANTEE FLASHBACK DATABASE;

Configuring appropriate undo retention and flashback settings is crucial for effectively using Oracle Flashback features to recover from logical errors and maintain data integrity.